Feature: Add a style

In order to customize the available styles in a document

As a developer using python-docx

I need a way to add a new style

Scenario Outline: Add a style

Given a document having known styles

When I call add_style('<name>', <type>, builtin=<builtin>)

Then the document has one additional style

And styles['<name>'] is a style

And style.type is <type>

And style.builtin is <builtin>

Examples: New style varieties